After previously speaking about seriously updating the graphics, and thus minimum specs within the near future, Blizzard have releaved many more "casual" gamers, by announcing the still rather low minimum specs for the next expansion, Wrath of The Lich King.

The minimum specs are:
Intel Pentium 4 1.3 GHz or AMD Athlon XP 1500+
512 MB of RAM (1GB for Vista)
3D graphics processor with Hardware Transform and Lighting with 32 MB VRAM (GeForce 2+, Radeon 7200+)

Aka, any PC made in the last...5 years or so?

Recomended is a fair bit higher, saying that a dual core with 1GB of ram and a Radeon X series/GeForce 7 card will make the game a much more pleasurable experience.